Transvascular medical lead

ABSTRACT

A medical electrical lead and methods of implanting medical electrical leads in lumens. Leads in accordance with the invention employ preformed biases to stabilize the lead within a lumen or lumen and to provide feedback to lead implanters.

CROSS REFERENCE TO RELATED APPLICATIONS

The present case claims the priority of U.S. Provisional ApplicationSer. No. 61/063,960, filed Feb. 7, 2008, entitled Muscle and NerveStimulation System. The disclosure of the provisonal application isincorporated by reference.

BACKGROUND

Electrical stimulation leads for providing medical therapy are beingused in an increasing number of applications. Leads have been implantedin patients' hearts, along the spinal column, and in other loctions todeliver appropriate therapy. Increasingly leads are implanted in veins,arteries, or other lumens to stimulate tissue near the lumens.

The implantation of electrical leads in lumens presents opportunitesbecause the leads can be fed into the patient's body and implantedwithout the surgery necessary to install nerve cuffs and othersurgically implanted electrodes. Implanting leads in lumens also reducesthe possibility of post-surgical trauma or damage to the tissue beingstimulated. Difficulties associated with implanting leads in lumensinclude issues with lead movement or migration and difficulty orientingthe lead and electrodes.

SUMMARY

In one embodiment in accordance with the invention, an elongate medicallead includes a lead body having a proximal portion and a distalportion. The proximal portion of the lead is configured to be connectedto an electrical signal generator. The lead further includes astabilizing section proximate the distal portion. The stabilizingsection of this embodiment has a first loop configured to turn in afirst direction, a second loop configured to turn in the same directionas the first loop, and a bend between the first and second loops. Insome embodiments, the loops are generally coplanar with each other. Inother embodiments the loops may be perpendicular to each other or atskew angles to each other. In some embodiments, a preformed bend in thelead assists in orienting the lead at the junction of two lumens or anatural bend or flex point in the lumens.

In another embodiment in accordance with the invention, an elongatemedical lead includes a lead body having a proximal portion and a distalportion. The proximal portion of the lead is configured to be connectedto an electrical signal generator. The lead further includes astabilizing section proximate the distal portion. The stabilizingsection of this embodiment has a first loop configured to turn in afirst direction, a second loop configured to turn in the same directionas the first loop, and a bend between the first and second loops. Thisembodiment includes an electrode on each of the loops that provide anextended bipole configuration when implanted. In some versions, the leadbody forms a lumen through which a guide wire or stylet may pass.

In another embodiment in accordance with the invention an elongatemedical lead has a proximal portion, a first distal portion having atleast one electrode, and a second distal portion also having at leastone electrode. In this embodiment the first distal portion is configuredto be retained in a subclavian vein of a patient and the second distalportion is configured to be retained in a brachiocephalic vein of apatient. An electrode on the first distal portion of this embodiment isconfigured to create an extended bipolar electric field with anelectrode on the second distal portion. This electric field may becapable of stimulating a phrenic nerve proximate the junction of thesubclavian and brachiocephalic veins. In some embodiments, the first andsecond distal portions may include loops preformed in the lead body.

Another elongate medical lead in accordance with embodiments of theinvention has a proximal end configured to be connected to animplantable medical device and a distal end having at least twoelectrodes. The distal end of the lead body includes a plurality ofloops. In some embodiments some loops are parallel to each other and inthe form of a coil.

In yet another embodiment in accordance with the invention, an elongatemedical lead has a lead body having a proximal portion, a first distalportion, and a second distal portion. There is a bend formed in the leadbody between the first distal portion and the second distal portion ofthis embodiment. At least one electrode is disposed on each of the firstand second distal portions. In some embodiments the first and seconddistal portions are loops, turning in either the same direction as eachother or in an opposite direction. In some embodiments the first andsecond distal portions together form a plurality of loops that areparallel to each other in the form of a coil.

Another embodiment involves a method of implanting a lead in a lumen.The lead is fed into a lumen to a desired location. The lead has apreformed bias proximate the distal end of the lead. There is aremovable guide wire or stylet within the lead, and the bias imparts ashape to the lead and guide wire combination. After being fed to thedesired location, the lead is rotated to a point where resistance torotation caused by the shape increases, and the guide wire or stylet isremoved from the lead while the lead is in a position of increasedrotational resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a patient with a lead implanted inaccordance with embodiments of the invention.

FIG. 2 is a view of a lead in accordance with an embodiment of theinvention in an unimplanted condition.

FIG. 3 is a view of a lead in accordance with an embodiment of theinvention.

FIG. 4 is a schematic representation of a lead in accordance withembodiments of the invention implanted at the junction of a patient'ssubclavian vein and right brachiocephalic vein.

FIG. 5 is a schematic representation of a lead in accordance withembodiments of the invention as it is in the process of being implantedproximate a junction of a patient's subclavian vein and rightbrachiocephalic vein.

FIG. 6 is a schematic representation of the lead of FIG. 5 as it is inthe process of being implanted proximate a junction of a patient'ssubclavian vein and right brachiocephalic vein.

FIG. 7 is a view of a lead in accordance with an embodiment of theinvention in an uninstalled condition.

FIG. 8 is a view of a lead in accordance with an embodiment of theinvention.

FIG. 9 is a schematic representation of a lead in accordance withembodiments of the invention as it is in the process of being implantedproximate a junction of a patient's subclavian vein and rightbrachiocephalic vein.

DETAILED DESCRIPTION

FIG. 1 is a schematic view of a patient with a lead implanted inaccordance with embodiments of the invention. FIG. 1 shows relevantelements of the patient's circulatory and nervous system. The displayedportion of the patient's circulatory system 10 includes a heart 20 and asuperior vena cava 30 and a right brachiocephalic vein 50 that returnblood to the heart from the body. Subclavian veins 40 return blood fromthe arms and interior jugular veins 60 return blood from the head.

Two phrenic nerves run from a patient's right and left upper spinalcolumn to the right and left hemi-diaphragms and act as the primarymotor nerves for each of the hemidiaphragms, which together make up thediaphragm 75. The right phrenic nerve 70 passes relatively close to thejunction of the right brachiocephalic vein 50 and the right subclavianvein 40. The right brachiocephalic vein empties into the superior venacava 30, which returns blood to the right atrium of the heart 20. Thetransition from the right brachiocephalic to the superior vena cava isimprecise, and references to the right brachiocephalic vein within thisdisclosure refer to both the right brachiocephalic and superior venacava unless otherwise indicated.

An implantable medical device 80 that may provide a stimulation signalor receive sensed signals to or from the patient's body is implantedsubcutaneously. A lead 90 in accordance with the invention is attachedto the implantable device 80 and fed into the subclavian vein 40 andfrom there into the right brachiocephalic 50.

FIG. 2 is a view of a lead in accordance with an embodiment of theinvention in an uninstalled condition. Lead 90 has a proximal portion100 and a distal portion 110. The proximal portion is configured to beconnected to an electrical signal generator 80 (not shown). The distalportion 110 includes a stabilizing structure comprising a first loop 120turning in a first direction, a pre-formed bend 130, and a second loop140 turning in the same direction as the first loop 120.

The lead 90 may be formed of polyurethane or other biocompatible andsuitable material. In some embodiments, the distal portion 110 of thelead may be made more stiff or inflexible to retain preformed biases orfor increased durability, for example. The proximal portion may be mademore flexible so that it does not exert or transmit excess force to thefixated end of the lead or for other reasons.

In another embodiment in accordance with the invention, a lead similarto the lead of FIG. 2 could be configured so that the second loop 140turns in the opposite direction of the first loop 120. There is reasonto believe that loops turning in opposite directions may be more stablein some applications by reducing the lead's ability to migrate down alumen. The two loops may “work against” each other during cardiac,respiratory, and limb movement that may induce motion. Lead stability inthis area can be challenging because of potential disruptions caused bya patient's coughing, sneezing, deep breathing, or other activities.

The embodiment of FIG. 2 includes at least one electrode 150. Theelectrode may be a ring electrode, for example, or any electrode knownin the art. The electrode is electrically connected to the proximal end100 of the lead, which is configured to electrically connect theelectrode 150 to a signal generator. In the optional embodiment shown inFIG. 2, there is an electrode on the first loop 120, one on the secondloop 140, and one at the distal end of the lead.

In its unimplanted condition, this embodiment is generally formed of twodimensional structures (loops, bends) formed in essentially the sameplane. From a lead fabrication perspective, it is often simpler tofabricate a “two-dimensional” lead consistently than to fabricate leadsthat require three-dimensional structures (spirals, biases in more thanone plane, etc.). The construction of leads with preformed shapes, suchas biases, loops, or bends, can be a complicated and imperfect process,especially considering the small size and relatively delicate nature ofmany of the lead elements.

In a typical fabrication process for a lead having pre-formed biases,the lead is held in a particular position by a rod or shaping mandrelplaced within lumen of the lead or by other means to retain the lead.The lead is then heated and cooled in this position to form the bend,loop, spiral, or other bias. The resulting shape of the lead formed bythis process is different than the shape of the rod or retention device.The lead itself will revert somewhat to its original shape or otherwiserespond a bit unpredictably to this and similar biasing processes, inpart due to the inherent shape memory of standard materials used tofabricate leads. A lead configured with generally two-dimensionalfeatures reacts more predictably and can be reproduced more consistentlybecause there are fewer variables to control. While this inventioncontemplates and includes “three dimensional” lead designs, it isbelieved that there are cost and quality benefits to usingtwo-dimensional structures when possible.

FIG. 3 is a view of a lead in accordance with an embodiment of theinvention. The lead in FIG. 3 is forced into a generally straightposition by a guide wire or stylet 160 installed within a lumen of thelead body. A first electrode of this embodiment is located at the distalend of the lead body. A second or middle electrode is approximately onecentimeter from the distal end of the lead body, and a third electrodeis approximately seven centimeters from the end of the lead body (or 6cm from the middle electrode). This lead is but one example of a lead inaccordance with embodiments of the invention, but the dimensions may berepresentative of a usable lead.

FIG. 4 is a schematic representation of a lead in accordance withembodiments of the invention implanted at the junction of a patient'ssubclavian vein and right brachiocephalic vein. The patient's phrenicnerve 70 runs proximate the junction of the subclavian vein 40 and theright brachiocephalic 50 vein.

The lead 90, as deployed, has distal portion 110 with a firststabilization element 170 generally located in the subclavian vein 40and a second stabilization element 180 generally located in the rightbrachiocephalic vein 50. In alternative embodiments, the lead 90 couldbe implanted with the first stabilization element 170 in the subclavianvein and the second 180 in the internal jugular vein 60. When implantedin the internal jugular vein 60, the lead may be configured to stimulatethe vagus nerve as well as or instead of the phrenic nerve. The lead 90could also be implanted on the patient's left side, either at thejunction of the left brachiocephalic and left subclavian or the leftsubclavian and left internal jugular vein. In fact, embodiments of leadsin accordance with the invention may be suitable for implantation at thejunction of any two suitable blood vessels or lumens or at a naturalbend or flex point in any lumen.

In this embodiment the stabilization elements are generallyspiral-shaped when implanted. In some embodiments in accordance with theinvention, the spirals begin as preformed loops, a coil of loops, oranother generally two-dimensional structure when the lead isconstructed. These loops become spirals or other three-dimensionalstructures as the lead is deployed in a vein. In other embodiments inaccordance with the invention, the lead includes preformed spirals.During installation the stabilization elements 170, 180 are straightenedwith a stylet, guide wire, catheter or other means while being fed to anappropriate location, and take on a generally spiral shape when deployedin a vein, lumen, or lumens.

For the purposes of this disclosure, a “spiral” is considered a leadbody that is longitudinally coiling around a fixed line or axis in aconstantly changing series of planes and is regarded asthree-dimensional. A lead formed in a loop that circles back upon itselfor a lead formed as a tightly wound coil are not, strictly speaking,two-dimensional or planar, but for purposes of this disclosure suchstructures will be considered and referred to as “two-dimensional.”Those of skill in the art will understand the distinction set forthherein.

The lead 90 of this embodiment has a plurality of electrodes 150disposed on the distal portion 110 of the lead. The stabilizationelements 170, 180 serve to stabilize and secure the lead within thevessel as well as to position at least one of the electrodes 150proximate a vessel wall. Preferentially, an electrode 150 will bepositioned near a point where the phrenic nerve passes by to enableeffective stimulation or sensing of the nerve. In some embodiments thelead 90 will be configured so that one electrode 150 is positionedproximate the wall of the subclavian vein 40 and another is positionedproximate the wall of the brachiocephalic vein 50 so that bipolarstimulation of the phrenic nerve 70 is possible between the twoelectrodes with a reasonably low level of native impedance.

The spirals of the stabilization elements 170 and 180 may turn in thesame direction as each other or in opposite directions. As discussedabove, they may be preformed portions of the lead that are initiallyconfigured as two-dimensional loops or three-dimensional spirals. Thedistal end 110 of the lead may be constructed to be relatively stifferthan the proximal portion to allow for more secure fixation by spiralsand/or other retaining means while the more flexible proximal portionmay be installed with some level of slack so that minimal force istransmitted through the lead body from the proximal to the distalportion, for example. The distal portion of the lead may be configuredwith other elements to improve fixation or ultimate stabilization. Theseelements may include, but are not limited to, one or more barbs, hooks,bumps, depressions, ridges or other surface irregularity, appropriatechemicals and/or materials and coatings promoting cellular formationsuch as extracellular matrix.

FIG. 5 is a schematic representation of a lead in accordance withembodiments of the invention as it is in the process of being implantedproximate a junction of a patient's subclavian vein and rightbrachiocephalic vein. The lead 90 is fed through the subclavian vein 40into the right brachiocephalic vein 50. The lead has a guide wire orstylet 160 within the lead body and includes at least one electrode 150.Other lead stiffening structures known in the art could be used insteadof, or in addition to, the guide wire 160. Despite the presence of theguide wire 160, preformed biases included at the distal end 110 of thelead body still convey a shape to the distal portion 110 of the lead 90.The lead as shown is oriented in the junction of the subclavian vein 40and the right brachiocephalic 50 in a position that generally conformsto the shape formed by the preformed biases.

FIG. 6 is a schematic representation of the lead of FIG. 5 as it is inthe process of being implanted proximate a junction of a patient'ssubclavian vein and right brachiocephalic vein. The lead 90 is fedthrough the subclavian vein 40 into the right brachiocephalic vein 50.The lead has a guide wire or stylet 160 within the lead body andincludes at least one electrode 150. In this representation the leadshape imparted by the lead biases does not conform to the junction ofthe subclavian vein 40 and the right brachiocephalic vein 50. Thisposition may be referred to as a high potential energy position, and theposition represented in FIG. 5 could be referred to as a low potentialenergy position.

The shape imparted to the lead 90 while on the guide wire or stylet 160provides for a simple and effective way to assist implanters withoptimal positioning of the distal end 110 of the lead 90. The implantercan rotate the lead from a low potential energy position (FIG. 5) to ahigh potential energy position (FIG. 6). When rotating the lead theimplanter will feel increased resistance to rotation as the leadapproaches a maximum potential energy position. If the implantercontinues to rotate the lead, it will “flip” from a high potentialenergy position to a low potential energy position. This flipping actionprovides even more feedback to the implanter regarding the position ofthe distal end 110 of the lead.

An implantation in accordance with embodiments of the invention mayinvolve an implanter rotating the lead 90 until the implanter can feelthe resistance to rotation increasing. As the resistance to rotationapproaches the point where the lead will flip from a high potentialenergy position to a low potential energy position, the implanter holdsthe lead in place in that high potential energy position and removes theguide wire or stylet. The feedback provided to the implanter allows fora more predictable configuration and orientation of the lead asimplanted and increases the likelihood that electrodes disposed on thelead will end up in desirable and effective locations.

In another implantation in accordance with embodiments of the invention,an implanter rotates the lead to a low potential energy position,perhaps just after a flip from a high potential energy position, andremoves the guide wire while holding the lead in that position. Theprinciple is the same. The fact that these various positions of thedistal end 110 of the lead are detectable by an implanter allows a leaddesigner to design leads and implantation procedures that improve theoutcome of the procedure and the effectiveness of any therapy deliveryelectrodes.

The shape of the distal portion of the lead may be imparted by preformedbiases in the lead as described above or by a biased, shaped, or bentguide wire or stylet inserted within a lumen in the lead body. A leaddesigner may coordinate the design of the stylet and the lead so thatthe shape creates the same kind of high and low potential energypositions for the stylet/lead combination and provides for similarimprovements in lead implantation.

FIG. 7 is a view of a lead in accordance with an embodiment of theinvention in an unimplanted condition. Lead 90 has a proximal portion100 and a distal portion 110. The proximal portion is configured to beconnected to an electrical signal generator 80 (not shown). The distalportion 110 includes a stabilizing structure comprising a first loop 120turning in a first direction, and a second loop 140 turning in theopposite direction from the first loop 120. The transition 190 from theloop 120 turning in one direction to the loop 140 turning in theopposite direction may act as a stabilizing feature as may the bend 130of the lead shown in FIG. 2. This stabilizing feature may help impart ashape to the lead that assists an implanter with orienting the distalend 110 of the lead during implantation. The stabilizing feature mayalso act as a secondary fixation element. The leads of FIGS. 2 and 7 maybe primarily retained by the loops that generally become spirals uponimplantation within a lumen. However, in cases where the leads areimplanted at the junction of two vessels, the transition 190 or bend 130may be designed to conform generally to the shape of the junction andprovide a secondary fixation feature.

As an example only, the diameter of the first loop 120 may be betweenabout 16 and 20 mm and the diameter of the second loop 140 may bebetween about 10 and 15 mm. These dimensions may vary based on patientsize, vessel size, implant location, and other considerations, and areprovided here only as examples. By understanding how the lead will reactin the implant site when properly positioned, lead designers canoptimize such variables as loop size and electrode location to increasethe likelihood of effective and stable positioning of electrodes.

As mentioned above, some leads in accordance with embodiments of theinvention impart shapes to guide wires and other stiffening members whenbeing implanted. This property can assist implanters in orienting thelead, and allows secondary stabilizing features like the bend 130 ortransition 190 or others that will occur to those of skill in the art tobe more effective.

FIG. 8 is a view of a lead in accordance with an embodiment of theinvention. Lead 90 has a proximal portion 100 and a distal portion 110.The proximal portion is configured to be connected to an electricalsignal generator 80 (not shown). The distal portion 110 includes astabilizing structure comprising a first loop 120 turning in a firstdirection, and a second loop 140 turning in the same direction as thefirst loop 120. The transition 200 from the loop 120 to the second loop140 turning may act as a stabilizing feature if the lead is implanted atthe junction of two lumens. This stabilizing feature may help impart ashape to the lead that assists an implanter with orienting the distalend 110 of the lead during implantation. The stabilizing feature mayalso act as a secondary fixation element.

FIG. 9 is a schematic representation of a lead in accordance withembodiments of the invention as it is in the process of being implantedproximate a junction of a patient's subclavian vein and rightbrachiocephalic vein. The lead 90 is fed through the subclavian vein 40into the right brachiocephalic vein 50. The lead has a guide wire orstylet 160 within the lead body and includes at least one electrode 150.Other lead stiffening structures known in the art could be used insteadof, or in addition to, the guide wire 160. Despite the presence of theguide wire 160, preformed biases included at the distal end 110 of thelead body still convey a shape to the distal portion 110 of the lead 90.The lead as shown is oriented in the junction of the subclavian vein 40and the right brachiocephalic 50 in a position that generally conformsto the shape formed by the preformed biases. The distal portion of thelead may be configured with other fixation assistance elements toimprove fixation or ultimate stabilization (shown schematically aselement 200). These elements may include, but are not limited to, one ormore barbs, hooks, bumps, depressions, ridges or other surfaceirregularity, appropriate chemicals and/or materials and coatingspromoting cellular formation such as extracellular matrix.

One skilled in the art will appreciate that the invention can bepracticed with embodiments other than those disclosed. The disclosedembodiments are presented for purposes of illustration and notlimitation, and the invention is limited only by the claims that follow.

What is claimed is:
 1. An elongate medical lead comprising: a. a leadbody having a proximal portion and a distal portion, the proximalportion configured to be connected to an electrical signal generator;and b. a stabilizing section formed of the lead body on the distalportion comprising; i. a first two-dimensional loop of the lead bodyconfigured to turn in a first direction; ii. a second two-dimensionalloop of the lead body configured to turn in the first direction; iii. abend in the lead body between the first and second loops wherein thefirst loop, the second loop, and the bend together comprise atwo-dimensional structure; and iv. a fixation assistance element on anexterior surface of the distal portion.
 2. The lead of claim 1, whereinthe first and second loops are generally coplanar with each other. 3.The lead of claim 1, wherein the first and second loops areperpendicular to each other.
 4. The lead of claim 1, wherein theproximal portion is more flexible than the distal portion.
 5. The leadof claim 1, further comprising at least one electrode located on thedistal portion of the lead.
 6. The lead of claim 5, comprising anelectrode on the first loop and at least two electrodes on the secondloop.
 7. The lead of claim 6, which is configured to provide a bipolarelectric field between the electrode on the first loop and at least oneof the electrodes on the second loop when implanted.
 8. The lead ofclaim 1, wherein the bend is configured to assist in orienting the leadat a junction of two lumens.
 9. The lead of claim 1, wherein the bend isconfigured to assist in orienting the lead at a junction of a subclavianvein and a brachiocephalic vein.
 10. The lead of claim 1, the lead bodyforming a lumen through which a guide wire may pass.
 11. The lead ofclaim 1, wherein the fixation assistance element is selected from thegroup consisting of a barb, a hook, an extracellular matrix, adepression, a ridge, and a bump.
 12. An elongate medical leadcomprising: a. a proximal portion; b. a first distal portion having atleast one electrode and comprising a two-dimensional loop prior todeployment or implantation; c. a second distal portion having at leastone electrode and comprising a two-dimensional loop prior to deploymentor implantation; d. the first distal portion being configured to beretained in a subclavian vein of a patient; e. the second distal portionbeing configured to be retained in a brachiocephalic vein of a patient;and f. the electrode of the first distal portion configured to create abipolar electric field with the electrode of the second distal portion.13. The lead of claim 12, wherein the loop of the first distal portionturns in one direction and the loop of the second distal portion turnsin an opposite direction.
 14. The lead of claim 12, wherein the loop ofthe first distal portion turns in one direction and the loop of thesecond distal portion turns in the one direction.
 15. The lead of claim12, wherein a diameter of the loop of the first distal portion isbetween 16 mm and 20 mm.
 16. The lead of claim 12, wherein a diameter ofthe loop of the second distal portion is between 10 mm and 15 mm. 17.The lead of claim 12, wherein the loops are parallel to each other. 18.An elongate medical lead comprising: a. a lead body having a proximalend configured to be connected to an implantable medical device, thelead body forming a first lumen through which a guide wire or stylet maypass; b. wherein a distal end of the lead body has at least twoelectrodes, the distal end of the lead body comprising a plurality ofloops, wherein each loop is configured to form a three-dimensionalspiral when deployed in a second lumen; and c. a fixation assistanceelement on an exterior surface of the distal end.
 19. The lead of claim18, wherein the plurality of loops of the distal end comprises threeloops.